1. Field of the Invention
This invention relates to methods of adding optical proximity correction data to data used to represent a mask pattern.
2. Description of the Related Art
When pattern dimensions become very small, such as less than 0.2 micrometers when projected on a wafer, it becomes necessary to add optical proximity correction, OPC, to the mask patterns. The mask patterns are typically received by semiconductor foundries from their customers in a the form of digital mask data files such as Graphical Design System II, GDSII, files or other formats of mask data files. The OPC data must then be added to the mask data files to form data files for masks having optical proximity correction.
U.S. Pat. No. 6,219,154 to Romano et al. describes an exposure control technique for imagesetting applications.
U.S. Pat. No. 5,663,893 to Wampler et al. describes a method of synthesizing correction features for a mask pattern. In this method the mask pattern data is divided into tiles of data.
U.S. Pat. No. 5,858,591 to Lin et al. describes optical proximity correction. In this method the data file in which the full description of the photoresist image, including optical proximity corrections, has been stored is split into two subfiles.
U.S. Pat. No. 5,994,009 to Tzu et al. describes a method for interlayer corrections for photolithographic patterns wherein the corrections correct for process induced proximity correction as well as optical proximity correction.
When pattern dimensions become very small, such as less than 0.2 micrometers when projected on a wafer, it becomes necessary to add optical proximity correction, OPC, to the mask patterns. In order to provide optical proximity correction the patterns must be altered by adding pattern width in certain mask regions and reducing pattern width in other mask regions so that the resulting image in a layer of resist on a wafer will be a faithful representation of the pattern. This is typically done by using OPC software with the digital data file representing the pattern to add optical proximity correction, OPC, to the mask pattern.
The mask patterns are typically received by semiconductor foundries from their customers in the form of GDSII data files. The OPC data must then be added to the GDSII data to form a data file for masks having optical proximity correction. This data file is then used for generating and checking the masks to be used in transferring the pattern to a layer of resist on a wafer. Typically adding the OPC data to the pattern file produces a very large file. Creating this large file is very time consuming. After the file has been created it must be converted into a writer format which is also very time consuming.
It is a principle objective of this invention to provide a method of adding OPC to patterns without the need for OPC software or large corrected pattern files.
It is another principle objective of this invention to provide a method of forming masks having OPC added to patterns without the need for OPC software or large corrected pattern files.
It is another principle objective of this invention to provide a method of inspecting masks having OPC added to patterns without the need for OPC software or large corrected pattern files.
These objectives are achieved by using a digital pattern data file for the pattern to be formed, a first OPC data file, and a second OPC data file. The first OPC data file represents a first optical proximity correction pattern which adds pattern width at exterior corners of the pattern. The first optical proximity correction pattern is a number of rectangles, usually squares. The second OPC data file represents a second optical proximity correction pattern which reduces pattern width at interior corners of the pattern. The second optical proximity correction pattern is also a number of rectangles, usually squares.
The final data file is formed by the logical operation of F=(A+B)xe2x88x92C, where A is the data file for the pattern to be reproduced in a layer of resist, B is the first OPC data file, and C is the second OPC data file. The symbol+indicates a logical OR and the symbolxe2x88x92indicates logical subtraction. The symbol F represents the final data used for the pattern having optical proximity correction.